Patients will be investigated with regard to their immunological reactivity against their own tumors (lung tumors, osteosarcoma, astrocytomas) using two in vitro assays: ATS-autologous tumor stimulation - which measures blastogenesis of lymphocytes exposed to the biopsy cells and ALC-autologous lymphocyte cytotoxicity exerted towards biopsy cells. In our past research a certain proportion of patients have exhibited such reactivities. In a further step the optimal conditions for generating cytotoxic cells in vitro by cocultivation with biopsy cells will be explored. It is possible that such in vitro generated reactive cells can be exploited in the future for immunotherapy. Tumor patients with the same and different histopathology will be tested for cross reactivity in the ATS and ALC assays. Preliminary experiments indicated that when biopsy preparations highly enriched for tumor cells are used, reactivity due to alloantigens does not occur. A prerequisite for the above delineated studies is the separation of biopsy into tumor and reactive cell components. The methodology has been worked out in our laboratory. This allows also the study of the nature of infiltration and the function of infiltrating cells in vitro. Thus information about in situ tumor immunity will also be obtained.